Polymeric hollow body articles have many uses including liquid handling and storage containers, hoses, tubing, and pipes. The use of polymeric hollow bodies, such as tubing and hoses, is increasing. One such application is motor vehicle fuel line tubing and hoses. At present these applications include the use of both monolayer and multilayer aliphatic polyamide (PA), high-heat rubber composites, and braided polytetrafluoroethylene (PTFE). At the same time there is also a trend toward higher temperatures in both diesel and passenger motor vehicle under-the-hood applications. While braided PTFE and high heat rubber composites can be used in these higher heat environments, the constructions are often complex and costly. The use aliphatic polyamide also has limitations in these high heat applications. In particular, PA12 has limitations with regard to both permeation of fuel and long term heat aging at the higher temperatures present in newer vehicles. Multilayer constructions are often subject to delamination, especially where fluoropolymer layers are present, and generally require special chemical bonding between layers as in U.S. Pat. No. 6,524,671.
There are different requirements for the vapor return line and the liquid fuel line in today's fuel systems. In the vapor line, one of the primary requirements is the barrier property to prevent vapors from escaping into the environment, as well as the long-term thermal and mechanical requirements. Included in the mechanical requirements are sufficient flexibility and impact strength for both fabrication and safety. In addition to the requirements for vapor lines, liquid lines also include the requirement that essentially no components in the fuel line contaminates the fuel, which could lead to problems, such as clogged fuel injectors.